Base station apparatus and communication control method

ABSTRACT

The object is achieved by providing a base station apparatus for performing time and frequency scheduling in uplink packet access with: an interference amount measurement part configured to measure an uplink interference amount for each interference amount measurement unit which comprises a predetermined period and a predetermined number of frequency blocks; an interference amount determination part configured to determine whether the uplink interference amount satisfies a predetermined condition; and an overload indicator reporting part configured to report an overload indicator to a neighboring cell when the predetermined condition is satisfied.

TECHNICAL FIELD

The present invention relates to a radio communication system. Moreparticularly, the present invention relates to a base station apparatusand a communication control method.

BACKGROUND ART

3GPP that is a standardization group of the third generation mobilecommunication system is studying a communication scheme that becomes anevolved version of W-CDMA, HSDPA and HSUPA, that is, 3GPP is studyingEvolved UTRA and UTRAN (Another name: Long Term Evolution or Super 3G,to be referred to as E-UTRA hereinafter) (refer to non-patent document1, for example).

Different from W-CDMA and the like, E-UTRA realizes all packet accessincluding radio sections. Especially, in the uplink, although thecomponent of the packet access is introduced in HSUPA which is anevolved version of W-CDMA, HSUPA uses circuit switching typecommunication based on dedicated channels. Uplink access schemes arelargely different between E-UTRA and earlier W-CDMA or HSUPA.

As main features, E-UTRA adopts all packet access, and adoptstime/frequency packet scheduling. Thus, in each cell, mobile stations towhich uplink radio resources are assigned are different for each TTI(Transmission Time Interval) and for each resource block (RB). As aresult, the other-cell interference amount applied to neighboring cellsdue to uplink transmission in a cell largely varies every TTI andlargely varies every RB.

FIG. 1 shows an example of variation of the interference amount for eachTTI. In FIG. 1, the horizontal axis indicates TTI, and the vertical axisindicates normalized interference power, and FIG. 1 shows Round Robin(RR) scheduling and Proportional Fairness (PF) scheduling. As a result,in both of the scheduling schemes, the uplink SINR(Signal-to-Interference plus Noise Power Ratio) largely varies, so thatcommunication quality deteriorates. Therefore, how the variation ofother-cell interference should be decreased is an issue.

As a method for decreasing the other-cell interference, a method using acontrol signal called Overload Indicator (OLI) is adopted in HSUPA andE-UTRA (refer to non-patent document 2, for example). As shown in FIG.2, each base station measures the uplink interference amount, andreports the interference amount to neighboring cells via a network usingOLI. The base station receiving OLI from a neighboring cell causes amobile station to decrease transmission power when it is determined thatthe interference amount exerted on the neighboring cell is large.Accordingly, the other-cell interference amount can be controlled, thatis, can be decreased, for example, so that throughput characteristics ofthe whole system and user throughput characteristics can be improved.

[Non-patent document 1] 3GPP TR25.814 (V7.1.0), “Physical Layer Aspectsfor Evolved UTRA”, September 2006.

[Non-patent document 2] 3GPP, TS 25.309, (V6.6.0), “FDD Enhanced UplinkOverall Description Stage 2,” March 2006.

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, the above-mentioned background technique has the followingproblem.

In E-UTRA, different from HSUPA, time/frequency scheduling is applied asmentioned above. Thus, the other-cell interference amount varies foreach TTI, and mobile stations which are assigned transmission vary foreach RB. Therefore, the interference amount largely varies. Thus, inorder to effectively control the other-cell interference amount, it isnecessary to report OLI for each TTI in the time axis direction, and foreach RB in the frequency axis direction. In E-UTRA, TTI is 1.0 msec.Thus, OLI needs to be reported 1000 times per one second. In addition,the number of RBs is 50, for example, in the case of a bandwidth of 10MHz. Thus, 50 pieces of OLI information on RB need to be reported inthis case. This causes large load not only for the network, but also forthe base station apparatus which performs transmit and receiveprocessing of OLI.

Therefore, in actuality, a method for lowering resolution of control isbeing studied. In the method, for example, OLI is reported based on anaverage interference amount every one second, instead of every TTI inthe time axis direction. In the frequency axis direction, for example,OLI is reported based on an interference amount averaged in the wholeband, instead of every RB.

However, in the control based on the average interference amount, thereis a problem in that the other-cell interference amount cannot beeffectively controlled in the E-UTRA uplink packet access in whichinterference amount largely varies every TTI and every RB.

In view of the above-mentioned problem, an object of the presentinvention is to provide a base station apparatus and a communicationcontrol method which can effectively control the other-cell interferenceamount based on a realistic control signal amount of the overloadindicator by decreasing the control signal amount of the overloadindicator while maintaining resolution of control in the time axisdirection and the frequency axis direction.

Means for Solving the Problem

In order to overcome the above problem, one aspect of the presentinvention relates to a base station apparatus for performing time andfrequency scheduling in uplink packet access, including:

an interference amount measurement part configured to measure an uplinkinterference amount for each interference amount measurement unit whichcomprises a predetermined period and a predetermined number of frequencyblocks;

an interference amount determination part configured to determinewhether the uplink interference amount satisfies a predeterminedcondition; and

an overload indicator reporting part configured to report an overloadindicator to a neighboring cell when the predetermined condition issatisfied.

Another aspect of the present invention relates to a communicationcontrol method in a base station apparatus for performing time andfrequency scheduling in uplink packet access, including:

an interference amount measurement step of measuring an uplinkinterference amount for each interference amount measurement unit whichcomprises a predetermined period and a predetermined number of frequencyblocks;

an interference amount determination step of determining whether theuplink interference amount satisfies a predetermined condition; and

an overload indicator reporting step of reporting an overload indicatorto a neighboring cell when the predetermined condition is satisfied.

EFFECT OF THE PRESENT INVENTION

According to an embodiment of the present invention, a base stationapparatus and a communication control method which can effectivelycontrol the other-cell interference amount based on a realistic controlsignal amount of the overload indicator can be realized by decreasingthe control signal amount of the overload indicator while maintainingresolution of control in the time axis direction and the frequency axisdirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing an example of variation ofinterference amount in each TTI;

FIG. 2 is an explanatory diagram showing an example of transmissionpower control;

FIG. 3 is an explanatory diagram showing a radio communication system ofan embodiment of the present invention;

FIG. 4 is a partial block diagram showing a base station apparatus of anembodiment of the present invention;

FIG. 5 is a flow diagram showing operation of the base station apparatusof an embodiment of the present invention;

FIG. 6 is a partial block diagram showing the base station apparatus ofan embodiment of the present invention;

FIG. 7 is a partial block diagram showing the base station apparatus ofan embodiment of the present invention;

FIG. 8 is a partial block diagram showing the base station apparatus ofan embodiment of the present invention; and

FIG. 9 is a partial block diagram showing the base station apparatus ofan embodiment of the present invention.

DESCRIPTION OF REFERENCE SIGNS

-   50 (50 ₁, 50 ₂) cell-   100 (100 ₁, 100 ₂, 100 ₃, . . . 100 _(n)) user apparatus-   200 (200 ₁, 200 ₂ . . . 200 ₁) base station apparatus-   202 radio part-   204 other-cell interference measurement part-   206 OLI transmission determination part-   208 OLI transmission part-   210 wired transmission line interface-   212 reference value control part-   214 reference value determination part-   216 other-cell interference amount measurement unit control part-   300 access gateway apparatus-   400 core network-   1000 radio communication system

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

In the following, embodiments of the present invention are describedwith reference to figures. In all of the figures for explainingembodiments, the same reference symbols are used for parts having thesame function, and repeated descriptions are not given.

A radio communication system including the mobile station and the basestation apparatus of an embodiment of the present invention is describedwith reference to FIG. 3.

The radio communication system 1000 is a system to which E-UTRA isapplied, for example. The radio communication system 1000 includes abase station apparatus (eNB: eNode B) 200 (200 ₁, 200 ₂ . . . 200 ₁, lis an integer of l>0) and a plurality of mobile stations 100 _(n) (100₁, 100 ₂, 100 ₃. . . 100 _(n), n is an integer and n>0). The basestation apparatus 200 is connected to an upper station, that is, anaccess gateway apparatus 300, for example, and the access gatewayapparatus 300 is connected to a core network 400. The mobile station 100_(n) is communicating with the base station apparatus 200 by E-UTRA in acell (50 ₁, 50 ₂). In the present embodiment, two cells are shown, but,more than two cells can be applied.

In the following, since the mobile stations (100 ₁, 100 ₂, 100 ₃, . . .100 _(n)) have the same configurations, functions and states, a mobilestation 100 _(n) is described unless otherwise mentioned. For the sakeof convenience of explanation, although the entity which communicateswith the base station apparatus by radio is the mobile station, it maybe a user apparatus (UE: User Equipment) including a mobile terminal anda fixed terminal more generally.

As radio access schemes, the radio communication system 1000 uses OFDM(orthogonal frequency division multiplexing) in the downlink, and usesSC-FDMA (single carrier—frequency division multiple access) in theuplink. OFDM is a multi-carrier transmission scheme in which a frequencyband is divided into a plurality of narrow frequency bands (subcarriers)so that transmission is performed by mapping data on each subcarrier.SC-FDMA is a single carrier transmission scheme that can decreaseinterference among terminals by dividing a frequency band for eachterminal and by using different frequency bands with each other by aplurality of terminals.

In the following, communication channels in the E-UTRA are described.

In the downlink, the physical downlink shared channel (PDSCH) shared byeach mobile station 100 _(n) and the physical downlink control channel(PDCCH) are used. The physical downlink control channel is also called adownlink L1/L2 control channel. User data, that is, a normal data signalis transmitted by the physical downlink shared channel. Also, thephysical downlink control channel transmits downlink (DL) schedulinginformation, acknowledgment information (ACK/NACK), uplink (UL)scheduling grant, overload indicator, transmission power control commandand the like.

The DL scheduling information includes, for example, ID of a userperforming communication using the physical downlink shared channel,information of transport format of the user data, that is, informationrelated to data size, modulation scheme and HARQ, and includesassignment information of downlink resource blocks, and the like.

The UL scheduling grant includes, for example, ID of a user performingcommunication using the physical uplink shared channel, information oftransport format of the user data, that is, information related to datasize and modulation scheme, and includes assignment information of theuplink resource blocks, transmission power control command, and thelike. The uplink resource block corresponds to frequency resources, andis also called a resource unit.

The acknowledgement information (ACK/NACK) is acknowledgementinformation on the uplink shared channel.

In the uplink, the physical uplink shared channel (PUSCH) shared by eachmobile station 100 _(n) and the physical uplink control channel areused. The physical uplink shared channel transmits user data, that is,the normal data signal. In addition, the physical uplink control channeltransmits downlink quality information (CQI: Channel Quality Indicator)used for scheduling processing for the physical downlink shared channeland for the adaptive modulation and coding scheme (AMC), and transmitsacknowledgment information of the physical downlink shared channel. Thecontents of the acknowledgment information are represented as either oneof Acknowledgement (ACK) indicating that a transmission signal has beenproperly received or Negative Acknowledgement (NACK) indicating that thesignal has not been properly received.

In addition to the CQI and the acknowledgement information, the physicaluplink control channel may transmit a scheduling request requestingresource assignment of the uplink shared channel, resource request inpersistent scheduling, and the like. The resource assignment of theuplink shared channel means that the base station apparatus reports,using the physical downlink control channel of a subframe, informationto the mobile station indicating that the mobile station is permitted toperform communication using the uplink shared channel in a followingsubframe.

The mobile station 100 _(n) communicates with an optimum base stationapparatus. In the example shown in FIG. 3, mobile stations 100 ₁ and 100₂ communicates with a base station apparatus 200 ₁, and a mobile station100 ₃ communicates with a base station apparatus 200 ₂. In this case,uplink transmission by the mobile stations 100 ₁ and 100 ₂ becomesinterference for the base station apparatus 200 ₂ which forms aneighboring cell. As described before, the other-cell interferencelargely varies since the mobile station changes every TTI and every RBdue to the uplink packet scheduling.

Thus, the base station apparatus 200 ₂ measures an uplink interferenceamount, and sends an overload indicator (OLI) to the base stationapparatus 200 ₁ via a network for reporting state of the measured uplinkinterference amount. The base station apparatus 200 ₁ that receives OLIfrom the base station apparatus 200 ₂ determines transmission power forcontrolling transmission power of a communicating mobile station. Thatis, when the base station apparatus 200 ₂ determines that an uplinkinterference amount from a mobile station (mobile station 100 ₁ and/or100 ₂, for example) residing in a cell covered by a base stationapparatus (base station apparatus 200 ₁, for example) which covers aneighboring cell other than the base station apparatus 200 ₂ is large,the base station apparatus 200 ₂ transmits OLI to the base stationapparatus 200 ₁ in order to decrease transmission power of the mobilestation 100 ₁ and/or 100 ₂.

Based on the OLI, the base station apparatus 200 ₁ determines that themobile stations 100 ₁ and 100 ₂ residing in the area covered by the basestation apparatus 200 ₁ exerts large interference on the base stationapparatus 200 ₂ other than the base station apparatus 200 ₁, so that thebase station apparatus 200 ₁ causes the mobile station 100 ₁ and/or 100₂. to decrease the transmission power.

The base station apparatus 200 of an embodiment of the present inventionis described with reference to FIG. 4.

The base station apparatus 200 of the present embodiment includes aradio part 202, an other-cell interference amount measurement part 204as an interference amount measurement part, an OLI transmissiondetermination part 206 as an interference amount determination part, anOLI transmission part 208 as an overload indicator reporting part, and awired transmission line interface 210. The wired transmission lineinterface is connected to a wired network.

When the base station apparatus 200 receives an uplink signal, which isthe physical uplink shared channel, for example, the base stationapparatus 200 performs reception processing in the radio part 202 so asto obtain a baseband signal. The received baseband signal is input tothe other-cell interference amount measurement part 204, so that theother-cell interference amount measurement part 204 measures theother-cell interference amount. For example, an uplink signal isreceived from a mobile station apparatus residing in an area covered bya base station apparatus other than the own base station apparatus. Themeasurement of the interference amount is performed for eachinterference amount measurement period and for each interference amountmeasurement unit frequency block, that is, the measurement of theinterference amount is performed every interference measurement unit.Typically, the measurement is performed every TTI and every RB. But, themeasurement may be performed every multiple TTIs and/or every multipleRBs in consideration of a control signal amount and a processing load inthe base station and the like. The other-cell interference amountmeasurement part 204 inputs the measured other-cell interference amountinto the OLI transmission determination part 206.

The OLI transmission determination part 206 determines whether to sendthe OLI to a neighboring cell based on measurement result of theother-cell interference amount. For example, based on a reference valuewhich is set beforehand, the OLI transmission determination part 206determines to report OLI only when the other-cell interference amount ineach interference amount measurement unit is equal to or greater thanthe reference value. The reference value is determined based on whetherit is necessary, for a base station apparatus in a neighboring cell, tocause a subject interference station (for example, a residing mobilestation) to decrease transmission power. For example, when theother-cell interference amount in each interference amount measurementunit is equal to or greater than the reference value, OLI indicatingdecreasing transmission power is transmitted to the neighboring cell.The neighboring cell performs control of transmission power based on thereceived OLI. In this case, the neighboring cell performs control tocause the residing mobile station to lower transmission power.Therefore, when other-cell interference amount in each interferenceamount measurement unit does not satisfy the reference value, it isdetermined that the base station apparatus of the neighboring cell doesnot need to consider OLI when determining transmission power of themobile station, so that OLI is not transmitted.

When the OLI transmission determination part 206 determines to reportOLI, the OLI transmission part 208 transmits OLI to the neighboringcell. As a result, OLI is reported to another base station apparatus viathe wired transmission line interface 210 and the wired network. Theother base station apparatus controls transmission power of the subjectinterference station based on the overload indicator transmitted fromthe neighboring cell.

Accordingly, the base station apparatus 200 ₂ need not report OLI whenit is determined that the base station apparatus 200 ₁ does not need toconsider OLI for determining transmission power of the residing mobilestation. Therefore, transmission load of control signals in the networkdue to OLI, and load for OLI transmit and receive processing can belargely decreased in the base station apparatus.

Even though the system is configured as mentioned above, OLI is reportedfor an interference amount measurement unit that exerts large effect inwhich the other-cell interference amount in each interference amountmeasurement unit is equal to or greater than the reference value. Thus,the effect for control the other-cell interference amount can besufficiently obtained.

In the present embodiment, an optimum value as a system parameter is setbeforehand as the reference value used for determining whether to reportOLI.

Next, operation of the base station apparatus in the radio communicationsystem in the present embodiment is described with reference to FIG. 5.

The base station apparatus receives an uplink signal from a mobilestation apparatus residing in an area covered by a base stationapparatus other than the own base station apparatus.

The other-cell interference amount measurement part 204 measures another-cell interference amount based on the uplink signal (step S502).

The OLI transmission determination part 206 determines whether theother-cell interference amount measured in step 5502 satisfies apredetermined condition (step S504). For example, it is determinedwhether the other-cell interference amount is equal to or greater than apredetermined reference value which is set beforehand.

When the other-cell interference amount satisfies the predeterminedreference value (step S504: Yes), that is, when the other-cellinterference amount is equal to or greater than a predeterminedreference value that is set beforehand, for example, the OLItransmission control part 206 determines to transmit an overloadindicator to a neighboring cell, and the OLI transmit part 208 transmitsthe overload indicator to the neighboring cell (step S506). After that,the process returns to step S502.

On the other hand, when the other-cell interference amount does notsatisfy the predetermined reference value (step S504: NO), that is, whenthe other-cell interference amount is less than a predeterminedreference value that is set beforehand, for example, the process returnsto step S502.

Next, a radio communication system of another embodiment of the presentinvention is described.

The configuration of the radio communication system of the presentembodiment is the same as the configuration of the radio communicationsystem described with reference to FIG. 3.

The base station apparatus 200 of the present embodiment is describedwith reference to FIG. 6.

The base station apparatus 200 of the present embodiment includes areference value control part 212 connected the OLI transmissiondetermination part 206 in addition to components of the base stationapparatus described with reference to FIG. 4. The reference valuecontrol part 212 receives a control signal from an upper station, forexample, from the access gateway apparatus 300.

The upper station 300 generates a control signal based on a trafficstate of the network and a state of the other-cell interference amountand the like, and transmits the generated control signal to each basestation apparatus. The control signal transmitted by the upper station300 is received by the base station apparatus 200, and is input into thereference value control part 212. The reference value control part 212controls a reference value based on the input control signal. Byperforming such processes, the reference value used for determiningwhether to report OLI can be flexibly changed according to the trafficstate of the network and the state of the other-cell interference amountand the like.

Next, a radio communication system of another embodiment of the presentinvention is described.

The configuration of the radio communication system of the presentembodiment is similar to the configuration of the radio communicationsystem described with reference to FIG. 3.

The base station apparatus 200 according to the present embodiment isdescribed with reference to FIG. 7.

The base station apparatus 200 of the present embodiment includes areference value determination part 214 connected the OLI transmissiondetermination part 206 in addition to components of the base stationapparatus described with reference to FIG. 4. The reference valuedetermination part 214 autonomously determines the reference value basedon a traffic state of the network and a state of the other-cellinterference amount and the like.

Based on the measurement result of the other-cell interference amountmeasured for each interference amount measurement unit, the referencevalue determination part 214 may determine a reference number N suchthat OLI is reported only for the top N (N is an integer of N>0) RBs inthe other-cell interference amount from the largest one among RBs(frequency blocks) in a TTI. In this case, the OLI transmissiondetermination part 206 determines to transmit OLI only for the top N RBsin the other-cell interference amount from the largest one among RBs ina TTI. Accordingly, OLI is transmitted to the base station apparatus 200₁ for only RBs which exert large effect, and OLI for other RBs is notreported. Therefore, it becomes possible to largely reduce networktransmission load for transmitting control signals due to OLI, andlargely reduce load for OLI transmit and receive processing in the basestation apparatus 200.

Even though the system is configured as mentioned above, OLI is reportedfor an interference amount measurement unit that exerts large effect inwhich the other-cell interference amount in each interference amountmeasurement unit is large. Thus, the effect for controlling theother-cell interference amount can be sufficiently obtained.

In addition, the reference value determination part 214 may set areference value and a reference number N, such that, in eachinterference amount measurement unit, OLI is reported for only the top N(N is an integer of N>0) RBs in the other-cell interference amount amongRBs in which the other-cell interference amount is equal to or greaterthan the reference value. Accordingly, when there are many interferenceamount measurement units in which the other-cell interference amountbecomes equal to or greater than the reference value, the interferenceamount measurement units for which OLI is reported can be limited to thetop reference number N. Therefore, it becomes possible to largely reducenetwork transmission load for transmitting control signals due to OLI,and reduce load for OLI transmit and receive processing in the basestation apparatus 200.

Even though the system is configured as mentioned above, OLI is reportedfor an interference amount measurement unit that exerts large effect inwhich the other-cell interference amount in each interference amountmeasurement unit is equal to or greater than the reference value. Thus,the effect for controlling the other-cell interference amount can besufficiently obtained.

Next, a radio communication system of another embodiment of the presentinvention is described.

The configuration of the radio communication system of the presentembodiment is similar to the configuration of the radio communicationsystem described with reference to FIG. 3.

The base station apparatus 200 according to the present embodiment isdescribed with reference to FIG. 8.

The base station apparatus 200 of the present embodiment includes another-cell interference amount measurement unit control part 216connected the other-cell interference amount measurement part 204 inaddition to components of the base station apparatus described withreference to FIG. 4.

The other-cell interference amount measurement unit control part 216changes time unit and/or frequency block unit for measuring theinterference amount, that is, the other-cell interference amountmeasurement unit control part 216 changes the interference amountmeasurement unit (OLI reporting unit). An optimum value as a systemparameter may be set beforehand as the interference amount measurementunit value.

Next, a radio communication system of another embodiment of the presentinvention is described.

The configuration of the radio communication system of the presentembodiment is similar to the configuration of the radio communicationsystem described with reference to FIG. 3.

The base station apparatus 200 according to the present embodiment isdescribed with reference to FIG. 9.

The base station apparatus 200 of the present embodiment is configuredsuch that the other-cell interference amount measurement unit controlpart 216 receives a control signal from an upper station, that is, fromthe access gateway apparatus 300, for example, in the base stationapparatus described with reference to FIG. 8.

The upper station 300 generates the control signal based on a trafficstate of the network and a state of the other-cell interference amount,and transmits the generated control signal to each base station. Basedon the control signal transmitted from the upper station 300, theother-cell interference amount measurement unit control part 216controls the interference amount measurement unit. In addition, theother-cell interference amount measurement unit control part 216 mayautonomously control the interference amount measurement unit based onthe traffic state of the network and the state of the other-cellinterference amount and the like.

For the sake of convenience of explanation, the present invention isdescribed by using some embodiments. But, classification into eachembodiment is not essential in the present invention, and equal to ormore than two embodiments may be used as necessary. While specificnumerical value examples are used to facilitate understanding of thepresent invention, such numerical values are merely examples, so thatany appropriate value may be used unless specified otherwise.

As described above, while the present invention is described withreference to specific embodiments, the respective embodiments are merelyexemplary, so that a skilled person will understand variations,modifications, alternatives, and replacements. For convenience ofexplanation, while the apparatus according to the embodiments of thepresent invention is explained using functional block diagrams, such anapparatus as described above may be implemented in hardware, software,or a combination thereof. The present invention is not limited to theabove embodiments, so that variations, modifications, alternatives, andreplacements are included in the present invention without departingfrom the spirit of the present invention.

The present international application claims priority based on Japanesepatent application No. 2007-126036, filed in the JPO on May 10, 2007,and the entire contents of the Japanese patent application No.2007-126036 is incorporated herein by reference.

1. A base station apparatus for performing time and frequency schedulingin uplink packet access, comprising: an interference amount measurementpart configured to measure an uplink interference amount for eachinterference amount measurement unit which comprises a predeterminedperiod and a predetermined number of frequency blocks; an interferenceamount determination part configured to determine whether the uplinkinterference amount satisfies a predetermined condition; and an overloadindicator reporting part configured to report an overload indicator to aneighboring cell when the predetermined condition is satisfied.
 2. Thebase station apparatus as claimed in claim 1, wherein the interferenceamount determination part determines that the predetermined condition issatisfied when the interference amount measured for each interferenceamount measurement unit is equal to or greater than a predeterminedreference value, and the predetermined reference value is any one of avalue set beforehand as a system parameter, a value set by a controlsignal sent from an upper apparatus, and a value autonomously controlledby the base station apparatus.
 3. The base station apparatus as claimedin claim 1, wherein the interference amount determination partdetermines that the predetermined condition is satisfied for the toppredetermined reference number N of interference amount measurementunits in the interference amount, from the largest interference amount,measured in each interference amount measurement unit, and thepredetermined reference number is any one of a value set beforehand as asystem parameter, a value set by a control signal sent from an upperapparatus, and a value autonomously controlled by the base stationapparatus.
 4. The base station apparatus as claimed in claim 1, whereinthe interference amount determination part determines that thepredetermined condition is satisfied for the top predetermined referencenumber N of interference amount measurement units in the interferenceamount from the largest interference amount, in which the interferenceamount measured in each of the interference amount measurement units isequal to or greater than a predetermined reference value, and each ofthe predetermined value and the predetermined reference number is anyone of a value set beforehand as a system parameter, a value set by acontrol signal sent from an upper apparatus, and a value autonomouslycontrolled by the base station apparatus.
 5. The base station apparatusas claimed in claim 1, wherein the interference amount measurement unitis set by any one of a system parameter set beforehand, a control signalsent from an upper apparatus, and the base station apparatus.
 6. Thebase station apparatus as claimed in claim 1, comprising: a transmissionpower control part configured to control transmission power of a subjectinterference station based on an overload indicator sent from aneighboring cell.
 7. A communication control method in a base stationapparatus for performing time and frequency scheduling in uplink packetaccess, comprising: an interference amount measurement step of measuringan uplink interference amount for each interference amount measurementunit which comprises a predetermined period and a predetermined numberof frequency blocks; an interference amount determination step ofdetermining whether the uplink interference amount satisfies apredetermined condition; and an overload indicator reporting step ofreporting an overload indicator to a neighboring cell when thepredetermined condition is satisfied.